This application claims the benefit of Korean Application Nos. 00-15031 and 01-6979 filed Mar. 24, 2000 and Feb. 13, 2001, respectively, in the Korean Patent Office, the disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus for optical recording/reproducing and a method therefor, and more particularly, to an auto laser diode power controlling apparatus for controlling a power level of a laser diode to be in an optimal state and a method therefor.
2. Description of the Related Art
Modern society is often called an information-oriented society or a multimedia society. In this society, high capacity recording media are required. Magnetic optical disc drives (MODDs) and digital versatile disc random access memories (DVD-RAMs), which are optical recording apparatuses, are used as the recording media. Since the optical recording apparatuses use laser diodes, the performance of equipment is determined by controlling the laser diodes to be in an optimal state. Since the types of recording pulses required by the respective optical recording devices are different, effective compensation for the different types of recording pulses is required.
FIG. 1 is a block diagram showing the structure of a conventional apparatus for controlling auto laser diode power level.
The apparatus shown in FIG. 1 includes an interface portion 110, a decoder 120, an address controller 130, a pulse generator 140, an auto laser diode power control (ALPC) block 150, a laser diode (LD) driver 160, a photodetector 170, and a time delay 180.
The interface portion 110 communicates with an external processor (not shown), for example, the microprocessor of a computer, and transmits information on recording/reproducing data, control data, and a use mode to the micro processor, and receives information on recording/reproducing data, control data, and a use mode from the micro processor. The decoder 120 includes an address decoder 121, a register 122, and a multiplexer 123 for selecting one among various registers included in the register 122. The address controller 130 may also include various registers and sub blocks for realizing functions and controls the entire apparatus.
The laser diode driver 160 is a device in which high speed switching can be performed, and can include an additional common use integrated circuit (IC) or an application specific integrated circuit (ASIC). The pulse generator 140 generates a signal for generating and controlling the respective recording pulses for forming a domain on a recording medium corresponding to data to be recorded. The time delay 180 is for delaying a signal from the pulse generator 140.
The ALPC block 150 detects a difference between a reference power level provided by the decoder 120 and the current power level provided from the photodetector 170 and controls the laser diode driver 160 according to the detection result.
The operation of the apparatus shown in FIG. 1 will be described. Since the interface portion 110 is different according to the structure of a particular system, the following explanation assumes that the functions of the interface portion 110 have already been performed.
The decoder 120 selects and maintains a target power level (read power, erase power, and peak power as a reference power level). The selected reference power level is input to the ALPC block 150, to which at least three reference power levels such as the read power, the erase power, and the peak power are input.
The respective reference power levels are digital to analog converted by a first D/A converter 151 and provided to a comparator 152. The photodetector signal output from the photodetector 170 is provided to the comparator 152 through a buffer (not shown). At this time, a signal to control the operation of the comparator 152 is generated by the pulse generator 140 and provided to the comparator 152 through the time delay 180.
An up/down counter 153 performs up or down counting according to the comparison result of the comparator 152. An output of the up/down counter 153 is selected by a second demultiplexer 154, converted into an analog to digital signal through a second D/A converter 155, and provided to the LD driver 160. A control signal for controlling the respective power levels provided by the ALPC block 150 and the respective power levels provided by the pulse generator 140 is input to the LD driver 160.
The apparatus shown in FIG. 1 uses the up/down counter 153 in performing controlling by comparing a reference power level with a fed back current power level. However, as the reproducing and recording speed of media becomes faster, controlling speed and a control range are restricted by the operation speed of the up/down counter 153.
Since the width of a recording pulse becomes shorter and more complicated as the recording speed of media increases, a compensation for these characteristics of the recording pulse is necessary.
To solve the above problems, it is an object of the present invention to provide an auto laser diode power controlling apparatus for controlling a laser diode to be in an optimal state.
It is another object of the present invention to provide an auto laser diode power controlling method of controlling a laser diode to be in an optimal state.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects of the present invention, there is provided an auto laser diode power controlling apparatus for controlling the output of a laser diode by comparing the current power level of an optical signal output by the LD with a reference power level and controlling the output of the LD according to the comparison result. A photo detector (PD) monitors the current power level of the optical signal output by the LD. A sampler and holder samples and holds the current power level output from the PD. A sample and hold control signal generator generates a sample and hold control signal which controls the sampling operation of the sampler and holder on the basis of a non return to zero inverted (NRZI) signal, and an operator compares the current power level sampled by the sampler and holder with the reference power level and controls the output of the LD according to the difference value.
To achieve another object, there is provided an auto laser diode power controlling method which controls the output of a laser diode by comparing the current power level with a reference power level and controlling the output of the LD according to the comparison result. The method comprises monitoring the current power level of an optical signal output from the LD with a photodetector (PD), sampling and holding the current power level output from the PD on the basis of a NRZI signal, comparing the sampled and held current power level with the reference power level and controlling the output of the LD according to a difference level between the sampled and held current power level and the reference level.